Design, synthesis and antimicrobial activities of 1-(4-oxo-3-(4-fluorophenyl)-3H-quinazolin-2-yl)-4-(substituted) thiosemicarbazide derivatives

Article abstract of DOI:10.4067/S0717-97072016000200002

A new series of 1-(4-oxo-3-(4-fluorophenyl)-3H-quinazolin-2-yl)-4-(substituted) thiosemicarbazides (AR1-AR10) were obtained by the reaction of 2-hydrazino-3-(4-fluorophenyl) quinazolin-4(3H)-one (6) with different dithiocarbamic acid methyl ester derivatives. The key intermediate 3-(4-fluorophenyl)-2-thioxo-2,3-dihydro-1H-quinazolin-4-one (4) was obtained by reacting 4-fluoroaniline (1) with carbon disulphide and sodium hydroxide in dimethyl sulphoxide to give sodium dithiocarbamate, which was methylated with dimethyl sulfate to yield the dithiocarbamic acid methyl ester (2) and condensed with methyl anthranilate (3) in ethanol yielded the desired compound (4) via the thiourea intermediate. The SH group of compound (4) was methylated for the favorable nucleophilic displacement reaction with hydrazine hydrate, which afford 2-hydrazino-3-(4-fluorophenyl)-3H-quinazolin-4-one (6). All synthesized compounds (AR1-AR10) were also screened for their antimicrobial activity against selective gram positive and gram negative by agar dilution method. In the present study compounds AR8 and AR9 were emerged as the most active compounds of the series.

Full text of DOI:10.4067/S0717-97072016000200002

J. Chil. Chem. Soc., 61, Nº 2 (2016)
DESIGN, SYNTHESIS AND ANTIMICROBIALACTIVITIES OF 1-(4-OXO-3-(4-FLUOROPHENYL)-3H-
QUINAZOLIN-2-YL)-4-(SUBSTITUTED) THIOSEMICARBAZIDE DERIVATIVES
V. ALAGARSAMY1 *, RAMGOPAL APPANI1, M. T. SULTHANA1, B. NARENDAR1, V. RAJA SOLOMON1
*1 Medicinal Chemistry Research Laboratory, MNR College of Pharmacy, Sangareddy.
ABSTRACT
A new series of 1-(4-oxo-3-(4-fluorophenyl)-3H-quinazolin-2-yl)-4-(substituted) thiosemicarbazides (AR1-AR10) were obtained by the reaction of
2-hydrazino-3-(4-fluorophenyl) quinazolin-4(3H)-one (6) with different dithiocarbamic acid methyl ester derivatives. The key intermediate 3-(4-fluorophenyl)-
2-thioxo-2,3-dihydro-1H-quinazolin-4-one (4) was obtained by reacting 4-fluoroaniline (1) with carbon disulphide and sodium hydroxide in dimethyl sulphoxide
to give sodium dithiocarbamate, which was methylated with dimethyl sulfate to yield the dithiocarbamic acid methyl ester (2) and condensed with methyl
anthranilate (3) in ethanol yielded the desired compound (4) via the thiourea intermediate. The SH group of compound (4) was methylated for the favorable
nucleophilic displacement reaction with hydrazine hydrate, which afford 2-hydrazino-3-(4-fluorophenyl)-3H-quinazolin-4-one (6). All synthesized compounds
(AR1-AR10) were also screened for their antimicrobial activity against selective gram positive and gram negative by agar dilution method. In the present study
compounds AR8 and AR9 were emerged as the most active compounds of the series.
Keywords: Quinazolinone, Substituted thiosemicarbazide, Anti-bacterial, Antitubercular activity.
thiosemicarbazides and thiosemicarbazones groups (Fig 1, III-IV) in different
heterocyclic moieties were also found to exhibit the antitubercular activity.7-15
The present work is an extension of our ongoing efforts towards developing
effective antitubercular and antimicrobial agents by a hybrid approach using
the quinazoline scaffold (Fig 1). In this approach two or more pharmacophores
are merged into a single molecule. Therefore, a single molecule containing
more than one pharmacophore, each pharmacophores may be addressing
the active site of targets and offer the possibility to selectivity, further it can
also reduce unwanted side effects.16 In the present study, we have placed the
substituted thiosemicarbazide moiety at the C-2 position and 4-fluorophenyl
ring at N-3 position of quinazoline ring17,18 and studied their antitubercular and
antibacterial activities against selected gram positive and negative bacteria.
INTRODUCTION
Tuberculosis (TB) is one of the leading causes of death all over the world.
Tuberculosis (TB) is an infection, primarily in the lungs (a pneumonia), caused
by bacteria called Mycobacterium tuberculosis. Emergence of multi drug
resistant tuberculosis (MDR-TB) makes the conditions most alarming.1,2 Some
of the MDR isolates are resistant to as many as seven of the commonly employed
antimycobacterial drugs.3 Quinazolines and condensed quinazolines received
the attention of medicinal chemists due to their potential biological activities.
Among the biological activities exhibited by quinazolines the antimicrobial
activities of 2,3-disubstituted quinazolines are promising.4 Literature survey
indicates that the quinazolines nucleus substituted at 2,3-position (Fig 1,
I, II) showed significant antitubercular activity.5,6 The pharmacophore like
Fig. 1. Hybrid approach design of 1-(4-oxo-3-(4-fluorophenyl)-3H-quinazolin-2-yl)-4-(substituted)thiosemicarbazide analogs.
Methods Chemistry
USA) and values were within the acceptable limits of the calculated values
Melting points (mp) were taken in open capillaries on Thomas Hoover
melting point apparatus (Thomas Hoover, USA) and are uncorrected. The IR
spectra were recorded in film or in potassium bromide disks on a Perkin-Elmer
(± 0.4%). The progress of the reaction was monitored on readymade silica
gel plates (Merck, Norway) using chloroform/methanol (9:1) as a solvent
system. Iodine was used as a developing agent. All chemicals and reagents
used in the synthesis were obtained from Aldrich (USA), Lancaster (USA) or
Spectrochem (India) and were used without further purification.
Synthesis of 3-(4-fluorophenyl)-2-thioxo-2,3-dihydro-1H-quinazolin-
4-one (4)
1
398 spectrometer (Perkin-Elmer, USA). The H spectra were recorded on a
DPX-300 MHz Bruker FT-NMR spectrometer (Bruker, USA). The chemical
shifts were reported as parts per million (δ ppm) tetramethylsilane (TMS) as an
internal standard. Mass spectra were obtained on a JEOL-SX-102 instrument
(JEOL, Japan) using fast atom bombardment (FAB positive). Elemental
analysis was performed on a Perkin-Elmer 2400 CHN analyzer (Perkin-Elmer,
A solution of 4-fluoroaniline 1 (0.02 mol) in dimethyl sulphoxide (10 mL)
was stirred vigorously. To this was added carbon disulphide (1.6 mL, 0.026
2856
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J. Chil. Chem. Soc., 61, Nº 2 (2016)
mol) and aqueous sodium hydroxide 1.2 mL (20 molar solution) drop wise
during 30 min with stirring. Dimethyl sulphate (0.02 mol) was added gradually
keeping the reaction mixture stirring in freezing mixture for 2 h. The reaction
mixture was then poured into ice water. The solid obtained was filtered, washed
with water, dried and recrystallized from ethanol. Methyl anthranilate (0.01
mol) and the above prepared N-(4-fluorophenyl)-methyl dithiocarbamic acid
(0.01 mol), were dissolved in ethanol (20 mL). To this anhydrous potassium
carbonate (100 mg) was added and refluxed for 23 h. The reaction mixture was
cooled in ice and the solid separated was filtered and purified by dissolving in
10% alcoholic sodium hydroxide solution and re-precipitated by treating with
dilute hydrochloric acid. The solid obtained was filtered, washed with water,
dried and recrystallized from ethanol. Yield = 83 %, mp 253-255 °C. IR: 3242
(NH), 1666 (C=O), 1218 (C=S) cm-1. 1H NMR (CDCl3) δ ppm: 6.45 (br s, 1H,
NH), 6.75-6.77 (m, 2H, ArH), 6.97-6.99 (d, J = 7.5 Hz, 2H, Ar-H), 7.26-7.28
1H, ArH), 8.42 (s, 1H, NH), 8.98 (s, 1H, NH), 10.53 (s, 1H, NH); 13C NMR
(CDCl ) δ ppm: 22.68, 25.79, 32.54, 52.75, 115.47, 120.56, 123.35, 123.68,
125.283, 127.85, 128.61, 130.81, 131.86, 138.75, 158.69, 162.45, 183.74; MS
(m/z): 412 ([M+H]+, 100); Anal. Calcd. for C21H22FN5OS: C 61.29, H 5.39, N
17.02; Found C 61.32, H 5.31, N, 17.08.
1-[4-oxo-3-(4-fluorophenyl)-3H-quinazolin-2-yl]-4-[benzyl]
thiosemicarbazide (AR2)
Yield = 79 %; mp 232-234 °C; IR (KBr) cm-1: 3321 (NH), 3295 (NH),
3264 (NH), 1692 (C=O), 1616 (C=N), 1216 (C=S); 1H NMR (CDCl ) δ ppm
: 1.51 (s, 1H, NH), 3.25 (s, 1H, NH), 4.56 (s, 2H, CH ), 6.61-6.643 (m, 2H,
ArH), 6.73-6.77 (m, 2H, ArH), 7.21-7.24 (d, J = 8.0 Hz,22H, Ar-H), 7.41-7.44
(d, J = 7.5 Hz, 2H, Ar-H), 7.56-7.59 (d, J = 8.0 Hz, 2H, Ar-H), 7.92-7.94 (d,
J = 8.0 Hz, 2H, Ar-H), 7.95-7.98 (m, 1H, ArH); 13C NMR (CDCl3) δ ppm:
49.68, 115.65, 120.68, 123.61, 123.74, 125.32, 125.72, 126.82, 127.42, 127.75,
128.41, 130.51, 131.45, 138.56, 140.35, 158.69, 161.87, 183.12; MS (m/z):
420 ([M+H+], 100); Anal. Calcd. for C22H18FN5OS: C 62.99, H 4.33, N 16.70;
Found C 65.85, H 4.74, N, 17.42.
(m, 1H, ArH), 7.65-7.67 (d, J = 7.5 Hz, 2H, Ar-H), 7.54-7.56 (m, 1H, ArH); 13
C
NMR (CDCl3) δ ppm: 120.61, 123.45, 123.78, 125.32, 127.72, 128.45, 130.79,
131.54, 138.75, 158.69, 160.18, 178.85; MS (m/z): 273 ([M+H]+, 100), 178
(58), 144 (56), 134 (40); Anal. Calcd. for C14H9FN2OS: C 61.75, H 3.33, N
10.29; Found C 61.65, H 3.38, N 10.17.
1-[4-oxo-3-(4-fluorophenyl)-3H-quinazolin-2-yl]-4-[phenyl]
thiosemicarbazide (AR3)
Synthesis of 3-(4-fluorophenyl)-2-(methylthio)quinazolin-4(3H)-one
(5)
Yield = 92 %; mp 276 - 278 °C; IR (KBr) cm-1: 3338 (NH), 3286 (NH),
3210 (NH), 1666 (C=O), 1600 (C=N), 1256 (C=S), 1136 (C-F); 1H NMR
(CDCl ) δ ppm: 6.51-6.54 (m, 2H, ArH), 6.82-6.85 (m, 2H, ArH), 7.12-7.15 (d,
J = 8.03Hz, 2H, Ar-H), 7.32-7.41 (d, J = 7.5 Hz, 2H, Ar-H), 7.60-7.63 (d, J = 8.0
Hz, 2H, Ar-H), 7.85-7.88 (d, J = 8.0 Hz, 2H, Ar-H), 7.91-7.93 (m, 1H, ArH),
8.72 (s, 1H, NH), 8.89 (s, 1H, NH), 10.53 (s, 1H, NH); 13C NMR (CDCl3) δ
ppm: 115.64, 120.54, 123.53, 123.68, 125.22, 125.39, 126.82, 127.35, 127.82,
128.72, 130.81, 131.86, 138.75, 140.35, 158.69, 162.75, 181.55; MS (m/z):
405 ([M+H+], 100); Anal. Calcd. for C21H16FN5OS: C 62.21, H 3.98, N 17.27;
Found C 62.18, H 3.95, N 17.19.
The 3-(4-fluorophenyl)-2-thioxo-2,3-dihydro-1H-quinazolin-4-one
4
(0.01 mol) was dissolved in 40 mL of 2% alcoholic sodium hydroxide solution.
To this dimethyl sulphate (0.01 mol) was added drop wise with stirring. The
stirring was continued for 1 h, the reaction mixture was then poured into ice
water. The solid obtained was filtered, washed with water, dried and recrystal-
lized from ethanol-chloroform (75:25) mixture. Yield = 81%, mp 153-155 °C;
IR: 1682 (C=O) cm-1; 1H NMR (CDCl3) δ ppm: 2.01 (s, 3H, SCH3), 6.65-6.67
(m, 2H, ArH), 6.95-6.97 (d, J = 7.5 Hz, 2H, Ar-H), 7.21-7.23 (m, 1H, ArH),
7.63-7.65 (d, J = 7.5 Hz, 2H, Ar-H), 7.64-7.66 (m, 1H, ArH); 13C NMR (CDCl3)
δ ppm: 12.58, 115.57, 120.56, 123.35, 125.28, 127.78, 127.85, 128.61, 130.81,
131.86, 138.75, 158.69, 162.15; MS (m/z): 287 ([M+H+], 100), 254 (48), 178
(45), 144 (52), 134 (33); Anal. Calcd. for C15H11FN2OS: C 62.92, H 3.87, N
9.78; Found C 62.95, H 3.92, N 9.82.
Synthesis of 2-hydrazino-3-(4-fluorophenyl)-3H-quinazolin-4-one (6)
The 3-(4-fluoro phenyl)-2-methylsulfanyl-3H-quinazolin-4-one 5 (0.01
mol) was dissolved in ethanol (25 mL). To this hydrazine hydrate (99%) (0.1
mol) and anhydrous potassium carbonate (100 mg) was added and refluxed
for 35 h. The reaction mixture was cooled and poured into ice water. The sol-
id so obtained was filtered, washed with water, dried and recrystallized from
chloroform-benzene (25:75) mixture. Yield = 72%, mp 174-176 °C. IR: 3310,
3226 (NHNH2), 1680 (C=O) cm-1; 1H NMR (CDCl3) δ ppm: 4.50 (s, 2H, NH2),
6.68-6.70 (m, 2H, ArH), 6.97-6.99 (d, J = 7.0 Hz, 2H, Ar-H), 7.31-7.33 (m,
1H, ArH), 7.73-7.75 (d, J = 7.0 Hz, 2H, Ar-H), 7.84-7.86 (m, 1H, ArH), 8.62
(br s, 1H, NH); 13C NMR (CDCl3) δ ppm: 115.47, 120.45, 123.54, 125.47,
127.76, 128.75, 130.65, 131.76, 138.75, 158.69, 160.53, 162.42; MS (m/z):
271 ([M+H]+, 100), 223 (55), 179 (48), 144 (57); Anal. Calcd. for C14H11FN4O:
C 62.22, H 4.10, N 20.73; Found C 62.62, H 4.17, N 20.67.
General procedure for synthesis of 1-(4-oxo-3-(4-fluorophenyl)-3H-
dihydroquinazolin-2-yl)-4-(substituted)thiosemicarbazides (AR1-AR10)
A solution of primary alkyl/aryl amine (0.02 mol) in dimethyl sulfoxide
(10 mL) was stirred vigorously. To this simultaneously carbon disulphide (1.6
mL) and aqueous sodium hydroxide 1.2 mL (20 molar solution) was added
drop wise during 30 min with stirring. Dimethyl sulphate (0.02 mol) was added
gradually by keeping the reaction mixture stirring in a freezing mixture and
continued for further 2 h. The reaction mixture was then poured into ice water
and the solid obtained was filtered washed with water, dried and recrystallized
from ethanol.
2-hydrazino-3-(4-fluoro phenyl)-3H-quinazolin-4-one (6) (2.32 g, 0.01
mol) and methyl-N-(substituted)dithiocarbamate (7) (0.01 mol) was dissolved
in ethanol and refluxed for 22-30 h (until the methyl mercapton evolution
ceases). After completion of the reaction the reaction mixture cooled to room
temperature. The solid obtained was filtered, dried and recrystallized from
ethanol. By adapting the above procedure the compounds AR1-AR10 were
prepared.
1-[4-oxo-3-(4-fluorophenyl)-3H-quinazolin-2-yl]-4-[2-methylphenyl]
thiosemicarbazide (AR4)
Yield = 86 %; mp 240-241 °C; IR (KBr) cm-1: 3338 (NH), 3270 (NH),
3242 (NH), 1655 (C=O), 1610 (C=N), 1250 (C=S), 1135 (C-F); 1H NMR
(CDCl3) δ ppm: 2.31 (s, 3H, CH3), 6.49-6.51 (m, 2H, ArH), 6.79 (br s, 1H, NH),
6.82-6.85 (m, 2H, ArH), 7.12-7.15 (d, J = 8.0 Hz, 2H, Ar-H), 7.32-7.36 (d, J =
7.5 Hz, 2H, Ar-H), 7.59-7.62 (d, J = 8.0 Hz, 2H, Ar-H), 7.75-7.78 (d, J = 8.0 Hz,
2H, Ar-H), 8.42 (br s, 1H, NH), 10.29 (br s, 1H, NH); 13C NMR (CDCl3) δ ppm:
13.58, 115.64, 120.54, 123.54, 123.63, 125.22, 125.42, 126.68, 127.82, 127.85,
128.61, 130.79, 131.86, 138.75, 138.85, 140.35, 158.69, 162.75, 182.63; MS
(m/z): 419 ([M+H+], 100); Anal. Calcd. for C22H18FN5OS: C 62.99, H 4.33, N
16.70; Found C 63.01, H 4.28, N 16.57.
1-[4-oxo-3-(4-fluorophenyl)-3H-quinazolin-2-yl]-4-[4-methylphenyl]
thiosemicarbazide (AR5)
Yield = 75 %; mp 225 - 226 °C; IR (KBr) cm-1: 3342 (NH), 3278 (NH),
1
3218 (NH), 1662 (C=O), 1262 (C=S), 1132 (C-F); H NMR (CDCl3) δ ppm:
2.31 (s, 3H, CH3), 6.51-6.53 (m, 2H, ArH), 6.75 (br s, 1H, NH), 6.72-6.75
(m, 2H, ArH), 7.17-7.20 (d, J = 7.5 Hz, 2H, Ar-H), 7.29-7.32 (d, J = 7.5 Hz,
2H, Ar-H), 7.59-7.62 (d, J = 7.5 Hz, 2H, Ar-H), 7.69-7.71 (d, J = 7.5 Hz, 2H,
Ar-H), 8.45 (br s, 1H, NH), 10.15 (br s, 1H, NH); 13C NMR (CDCl3) δ ppm:
13.58, 115.64, 120.43, 123.56, 123.62, 125.75, 125.85, 126.68, 127.82, 127.93,
128.61, 130.79, 131.86, 138.69, 138.91, 140.35, 158.69, 162.75, 182.35; MS
(m/z): 419 ([M+H+], 100); Anal. Calcd. for C22H18FN5OS: C 62.99, H 4.33, N
16.70; Found C 62.89, H 4.31, N 16.62.
1-(3-(4-fluorophenyl)-4-oxo-3,4-dihydroquinazolin-2-yl)-4-(3-
methoxyphenyl)thiosemicarbazide (AR6)
Yield = 80 %; mp 190-192 °C; IR (KBr) cm-1: 3340 (NH), 3280 (NH),
3223 (NH), 1660 (C=O), 1605 (C=N), 1270 (OCH3), 1260 (C=S), 1130 (C-F);
1HNMR (CDCl ) δ ppm : 3.71 (s, 3H, OCH3), 6.61-6.63 (m, 2H, ArH), 6.79
(br s, 1H, NH),36.82-6.85 (m, 2H, ArH), 7.21-7.24 (d, J = 7.0Hz, 2H, Ar-H),
7.32-7.35 (d, J = 7.0 Hz, 2H, Ar-H), 7.62-7.66 (d, J = 8.0 Hz, 2H, Ar-H), 7.71-
7.74 (d, J = 7.0 Hz, 2H, Ar-H), 8.45 (br s, 1H, NH), 10.25 (br s, 1H, NH); 13
C
NMR (CDCl ) δ ppm: 54.75, 109.87, 115.47, 117.85, 120.48, 123.48, 123.75,
125.53, 127.321, 127.75, 128.75, 129.57, 129.89, 130.81, 131.46, 137.57,
138.75, 158.69, 162.42, 181.53; MS (m/z): 435 ([M+H+], 100); Anal. Calcd.
for C22H18FN5O2S: C 60.68, H 4.17, N 16.08; Found C 60.62, H 4.18, N, 16.04.
1-(3-(4-fluorophenyl)-4-oxo-3,4-dihydroquinazolin-2-yl)-4-(4-
methoxyphenyl)thiosemicarbazide (AR7)
1-[4-oxo-3-(4-fluorophenyl)-3H-quinazolin-2-yl]-4-[cyclohexyl]
thiosemicarbazide (AR1)
Yield = 84 %; mp 220- 222 °C; IR (KBr) cm-1: 3319 (NH), 3227 (NH),
3266 (NH), 1684 (C=O), 1608 (C=N), 1218 (C=S), 1100 (C-F); 1HNMR
(CDCl ) δ ppm : 3.75 (s, 3H, OCH3), 6.59-6.61 (m, 2H, ArH), 6.69 (br s, 1H,
NH), 63.81-6.83 (m, 2H, ArH), 7.23-7.26 (d, J = 7.5 Hz, 2H, Ar-H), 7.31-7.34 (d,
J = 8.0 Hz, 2H, Ar-H), 7.61-7.64 (d, J = 7.5 Hz, 2H, Ar-H), 7.73-7.76 (d, J = 7.0
Hz, 2H, Ar-H), 8.55 (br s, 1H, NH), 10.31 (br s, 1H, NH); 13C NMR (CDCl3) δ
Yield = 83 %; mp 192-193 °C; IR (KBr) cm-1: 3356 (NH), 3283 (NH),
3243 (NH), 1660 (C=O), 1605 (C=N), 1210 (C=S); 1H NMR (CDCl3) δ ppm:
1.40-1.62 (m, 6H, CH ), 1.82-1.84 (m, 2H, CH2), 1.91-1.93 (m, 2H, CH2), 2.84
(s, 1H, CH), 6.79-6.822 (m, 2H, ArH), 7.11-7.14 (m, 1H, ArH), 7.39-7.41 (d,
J = 7.0 Hz, 2H, Ar-H), 7.45-7.48 (d, J = 7.0 Hz, 2H, Ar-H), 7.91-7.93 (m,
2857

J. Chil. Chem. Soc., 61, Nº 2 (2016)
ppm: 54.89, 108.97, 115.23, 117.71, 120.43, 123.18, 123.68, 124.53, 126.33,
126.84, 127.85, 129.57, 128.99, 130.81, 131.46, 137.57, 138.75, 158.69,
162.42, 181.25; MS (m/z): 435 ([M+H+], 100); Anal. Calcd. for C22H18FN5O2S:
C 60.68, H 4.17, N 16.08; Found C 60.72, H 4.08, N, 16.11.
Cytotoxicity profile of the tested compounds
For cytotoxic assay with HeLa, approximately 10,000 cells were seeded
with 0.1 mL RPMI 1640 culture medium per well of the 96-well micro plates.
HeLa cells were preincubated for 48 h without the test substances. The solutions
of the compounds of the corresponding concentrations were applied carefully
on the monolayers of HeLa cells after the preincubation time. The monolayers
of the adherent HeLa cells were fixed by glutaraldehyde and stained with a
0.05% solution of methylene blue for 15 min. After gently washing, the stain
was eluted by 0.2 mL of 0.33N HCl in the wells. The optical densities were
measured at 630 nm in a micro plate reader. In general, compounds showed no
significant cytotoxic effect at tested concentration.24
1-[4-oxo-3-(4-fluorophenyl)-3H-quinazolin-2-yl]-4-[4-chlorophenyl]
thiosemicarbazide (AR8)
Yield = 88 %; mp 262-264 °C; IR (KBr) cm-1: 3288 (NH), 3269 (NH), 3203
1
(NH), 1682 (C=O), 1610 (C=N), 1258 (C=S), 1122 (C-F); H NMR (CDCl3)
δ ppm: 6.42-6.45 (m, 2H, ArH), 6.53-6.55 (m, 1H, ArH), 7.22-7.24 (d, J = 8.0
Hz, 2H, Ar-H), 7.42-7.46 (d, J = 8.0 Hz, 2H, Ar-H), 7.73-7.77 (d, J = 7.5 Hz,
2H, Ar-H), 7.80-7.83 (d, J = 7.5 Hz, 2H, Ar-H), 7.92-7.94 (m, 1H, ArH), 8.63
(br s, 1H, NH), 8.92 (br s, 1H, NH), 10.63 (br s, 1H, NH); 13C NMR (CDCl ) δ
ppm: 115.34, 121.39, 122.37, 123.44, 124.82, 125.87, 126.74, 127.22, 127.385,
128.61, 130.81, 131.86, 138.75, 139.45, 158.69, 161.79, 181.61; MS (m/z): 440
([M+H+], 100); Anal. Calcd. for C21H15ClFN5OS: C 57.34, H 3.44, N 15.92;
Found C 57.35, H 3.34, N 15.88.
RESULTS AND DISCUSSION
Chemistry
Synthetic route depicted in Scheme 1 outline the chemistry part of the
present work. The key intermediate 3-(4-fluorophenyl)-2-thioxo-2,3-dihydro-
1H-quinazolin-4-one (4) was obtained by reacting 4-fluoroaniline (1) with
carbon disulphide and sodium hydroxide in dimethyl sulphoxide to give
sodium dithiocarbamate, which was methylated with dimethyl sulfate to afford
the dithiocarbamic acid methyl ester (2). Compound 2 on reflux with methyl
anthranilate (3) in ethanol yielded the desired 3-(4-fluorophenyl)-2-thioxo-2,3-
dihydro-1H-quinazolin-4-one (4) via the thiourea intermediate in good yield
(83%). The product obtained was cyclic and not an open chain thiourea 3a.
The 3-(4-fluorophenyl)-2-methylsulfanyl-3H-quinazolin-4-one 5 was obtained
by dissolving 4 in 2% alcoholic sodium hydroxide solution and methylating
with dimethyl sulphate with stirring at room temperature. Nucleophilic
displacement of methylthio group of 5 with hydrazine hydrate was carried
out using ethanol as solvent to afford 2-hydrazino-3-(4-fluorophenyl)-3H-
quinazolin-4-one 6. The long duration of reaction (35 h) required might be due
to the presence of bulky aromatic ring at position 3, which might have reduced
the reactivity of quinazoline ring system at C-2 position. The title compounds
1-(4-oxo-3-(4-fluorophenyl)-3H-dihydroquinazolin-2-yl)-4-(substituted)
thiosemicarbazides (AR1-AR10) were obtained by the condensation of amino
group of 2-hydrazino-3-(4-fluorophenyl)-3H-quinazolin-4-one (6) with a
variety of methyl ester of dithiocarbamic esters. The formation of title product
is indicated by the disappearance of peak due to NH, NH2 of the starting
material in IR and 1H NMR spectrum of all the compounds AR1-AR10. The IR
and 1H NMR spectrum of these compounds showed the presence of peaks due
to thiosemicarbazides, carbonyl (C=O), NH and aryl groups. The mass spectra
of the title compounds showed molecular ion peaks corresponding to their
molecular formulae. In mass spectrum of compounds AR1-AR10 a common
peak at m/z 144 corresponding to quinazolin-4-one moiety appeared. Elemental
(C, H, N) analysis satisfactorily confirmed elemental composition and purity of
the synthesized compounds.
4 - ( 4 - c h l o ro p h e n y l ) - 1 - ( 3 - ( 4 - f l u o ro p h e n y l ) - 4 - o x o - 3 , 4 -
dihydroquinazolin-2-yl)thiosemicarbazide (AR9)
Yield = 82 %; mp 242-245 °C; IR (KBr) cm-1: 3352 (NH), 3310 (NH),
3210 (NH), 1691 (C=O), 1615 (C=N), 1220 (C=S); 1H NMR (CDCl3) δ ppm:
6.72-6.75 (m, 2H, ArH), 6.92-6.95 (d, J = 7.5 Hz, 2H, Ar-H), 7.32-7.36 (d, J =
8.0 Hz, 2H, Ar-H), 7.63-7.67 (d, J = 7.5 Hz, 2H, Ar-H), 7.75-7.78 (d, J = 7.5
Hz, 2H, Ar-H), 7.92-7.94 (m, 2H, ArH), 8.45 (br s, 1H, NH), 8.75 (br s, 1H,
NH), 10.35 (br s, 1H, NH); 13C NMR (CDCl3) δ ppm: 115.25, 121.89, 122.57,
123.11, 124.73, 125.87, 126.74, 127.22, 127.85, 128.61, 130.75, 131.86,
138.75, 139.45, 158.69, 161.79, 182.61; MS (m/z): 451 ([M+H+], 100); Anal.
Calcd. for C21H15FN6O3S: C 55.99, H, 3.36, N 18.66; Found C 57.35, H 3.34,
N 15.88.
1-[4-oxo-3-(4-fluorophenyl)-3H-quinazolin-2-yl]-4-[pyridin-2-yl]
thiosemicarbazide (AR10)
Yield = 78 %; mp 180-182 °C; IR (KBr) cm-1: 3350 (NH), 3310 (NH),
3223 (NH), 1680 (C=O), 1614 (C=N), 1200 (C=S); 1H NMR (CDCl3) δ ppm:
6.41-6.44 (m, 1H, ArH), 6.83-6.85 (m, 2H, ArH), 7.21-7.24 (d, J = 7.5 Hz,
2H, Ar-H), 7.40-7.43 (d, J = 8.0 Hz, 2H, Ar-H), 7.61-7.65 (d, J = 7.5 Hz, 2H,
Ar-H), 7.80-7.83 (d, J = 7.5 Hz, 2H, Ar-H), 7.90-7.93 (m, 1H, ArH), 8.83 (br
s, 1H, NH), 9.03 (br s, 1H, NH), 10.32 (br s, 1H, NH); 13C NMR (CDCl3) δ
ppm: 108.75, 112.89, 115.25, 120.48, 123.51, 123.25, 125.42, 127.53, 128.61,
130.81, 131.86, 137.89, 138.75, 147.75, 157.85, 158.69, 161.78, 181.25; MS
(m/z): 407 ([M+H+], 100); Anal. Calcd. for C20H15FN6OS: C 59.10, H 3.72, N
20.68, Found C 59.15, H 3.75, N 20.72.
Pharmacology
Antibacterial activity
Evaluation of antibacterial activity determined by agar dilution method.10,11
.
The standard strains were procured from the American Type Culture Collection
(ATCC), Rockville, USA, and the pathological strains were procured from the
Department of Microbiology, MNR Medical College, Sangareddy, India. The
antibacterial activity of the synthesized compounds was screened against the
following bacterial strains: P. vulgaris ATCC 9484, S. typhimurium ATCC
33068, K. pneumoniae ATCC 13883, E. tarda, P. aeruginosa ATCC 2853, B.
subtilis ATCC 6051, and S. paratyphi. All bacteria were grown on Muller–
Hinton Agar (Hi-media) plates (37 °C, 24 h) and the minimum inhibitory
concentration (MIC) was considered to be the lowest concentration that
completely inhibited the growth on agar plates, disregarding a single colony
or faint haze caused by the inoculums.19, 20 The MIC of the test compounds was
compared with the reference drug ciprofloxacin. The values are mentioned in
Table 1 calculated from at least three different experiments in duplicate.
Antitubercular activity
10 fold serial dilutions of each test compound/drug were incorporated into
Middle brook 7H11 agar slants with OADC Growth Supplement. Inoculums
of M. tuberculosis H37RV were prepared from fresh Middle brook 7H11
agar slants with OADC Growth Supplement adjusted to 1 mg/mL in Tween
80 (0.05% W/V) saline diluted to 10-2 to give a concentrate of approximately
107 cfu/mL. A 5µL amount of bacterial suspension was spotted into 7H11
agar tubes containing 10-fold serial dilutions of drug per mL. The tubes were
incubated at 37 ºC, and final readings were recorded after 28 days. Tubes
having the compounds were compared with control tubes where medium alone
was incubated with H37RV. The concentration at which complete inhibition
of colonies occurred was taken as active concentration of test compound. The
MIC is defined as the minimum concentration of compound required to give
complete inhibition of bacterial growth.21-23 The MIC of the test compounds
was compared with the reference drug gatifloxacin.
Antitubercular activity
The synthesized compounds were screened for their in vitro
antimycobacterial activity against M. tuberculosis strain H37RV. The results are
expressed in terms of Minimum Inhibitory Concentration (MIC). The results of
antimycobacterial activity depicted in Table 1, indicates that the test compounds
inhibited the growth of Mycobacterium in varying degree. Compounds with
aliphatic substituents showed lesser antitubercular activity over the aryl and
heteroaryl substituents. The compounds with electron withdrawing substituent
on the aryl ring showed better activity over the unsubstituted or electron
donating substituent on the aryl ring. Among the test compounds, 1-(4-oxo-3-
(4-fluorophenyl)-3H-quinazolin-2-yl)-4-(4-chlorophenyl) thiosemicarbazides
(AR8) and as well as 1-(4-oxo-3-(4-fluorophenyl)-3H-quinazolin-2-yl)-4-(4-
nitrophenyl)thiosemicarbazides (AR9) exhibited the antitubercular activity at
the minimum microgram (3 µg/mL) concentration.
2858

J. Chil. Chem. Soc., 61, Nº 2 (2016)
Scheme 1. Synthesis of 1-(4-oxo-3-(4-fluorophenyl)-3H-quinazolin-2-yl)-4-(substituted) thiosemicarbazides.
Table 1: Antitubercular and antibacterial activity of synthesized compounds (A1-A10).
Test Compounds
(MIC in µg/ml)
Microorganisms
M. tuberculosis
S. typhi
63
63
26
125
32
26
63
63
63
63
63
63
125
63
63
63
6
13
125
63
6
13
63
32
125
63
32
32
63
32
32
63
3
3
6
1
4
2
1
1
1
1
1
1
1
1
125
63
125
125
32
8
8
32
32
63
32
16
16
16
16
32
16
E. coli
63
8
8
S. flexneri
63
63
63
125
63
16
16
16
32
32
8
16
16
16
16
16
16
16
8
P. vulgaris
63
63
125
63
32
Enterobacter spp.
K. pneumonia
S. enteritidis
B. subtilis
125
125
125
63
125
63
63
16
125
63
63
63
63
125
32
125
63
125
63
125
32
S. flexneri
125
32
125
32
63
16
32
P. aeruginosa
63
32
32
*Gatifloxacin used as a reference standard against M. tuberculosis whereas Ciprofloxacin used as a reference standard for other bacteria.
2859

J. Chil. Chem. Soc., 61, Nº 2 (2016)
Antibacterial activity
21- D. Sriram, P. Yogeeswari, J.S. Basha, D. R. Radha and V. Nagaraja, Bioorg.
Med. Chem., 13, 5774 (2005).
22- P. Shanmugavelan, S. Nagarajan, M. Sathishkumar, A. Ponnuswamy, P.
Yogeeswari and D. Sriram, Bioorg. Med. Chem. Lett., 21, 7273 (2011).
23- J. Kunes, J. Bazant, M. Pour, K. Waisser, M. Slosárek and J. Janota, IL
Farmaco., 2000, 55, 725.
Among the different substituents at C-2 position of the quinazolin-2-yl,
aryl and heteroaryl substitutents exhibited better activity over the aliphatic
cyclic substituents. Compounds with electron withdrawing substituents like
–Cl and –NO showed better activity over the unsubstituted and electron
donating subst2ituents. Compounds AR8 and AR9 were emerged as the most
active compounds of the series. Compound AR8 shown most potent activity
against S. typhi, E.coli and B. subtilis. While the compound AR9 showed most
potent activity against S. typhi, E.coli and P. aeruginosa.
24- V. Alagarsamy, V.R. Solomon, R. Meena, K.V. Ramaseshu, K.
Thirumurugan and S. Murugesan, Med. Chem., 3, 67 (2007).
CONCLUSION
In summary, synthesis of new series of 1-(4-oxo-3-(4-fluorophenyl)-
3H-dihydroquinazolin-2-yl)-4-(substituted) thiosemicarbazides have been
described. These derivatives have exhibited significant antibacterial activity
against the various gram positive and gram negative bacteria including M.
tuberculosis. Among the series, compound AR8 shown most potent activity
against S. typhi, E.coli and B. subtilis. While the compound AR9 showed most
potent activity against S. typhi, E.coli and P. aeruginosa. The test compounds,
AR8 and AR9 exhibited the antitubercular activity at the minimum microgram
(3 µg/mL) concentration and offers potential for further optimization and
development to new antitubercular agents.
ACKNOWLEDGEMENTS
The authors gratefully acknowledge the Central Instrumentation Facility,
IIT Chennai, India for the spectral analysis of the compounds used in this study;
Dr. D. Sriram, Birla Institute of Technology & Sciences, Hyderabad campus for
performing antitubercular screening of the test compounds.
Conflict of Interest Statement
The authors report no conflicts of interest to declare in connection with the
contents of this manuscript.
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